The exception taglib, AxKit::XSP::Exception,
is used to catch exceptions. The
syntax is very simple: rather than allowing different types of
exceptions, it is currently a very simple
try/catch block. To use the
exceptions taglib, the following has to be added to
httpd.conf:

AxAddXSPTaglib AxKit::XSP::Exception

Then you can implement form validation using exceptions, as Example E-6 demonstrates.